Direct comparison
MDI vs DPI: Differences in Design and Delivery
MDI vs DPI: propellant, dose metering, components and spacer compatibility compared, plus FDA combination-product status. Design-level, not medical advice.
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How do MDI (pressurized metered dose inhaler), DPI (dry powder inhaler) compare side by side?
The table below compares MDI (pressurized metered dose inhaler), DPI (dry powder inhaler) across 10 procurement-relevant dimensions, from energy source and propellant through source.
Side-by-side comparison
| Dimension | MDI (pressurized metered dose inhaler) | DPI (dry powder inhaler) |
|---|---|---|
| Energy source and propellant | MDI products use energy stored in a liquefied gas propellant under pressure; the formulation contains one or more propellants (FDA draft guidance). | DPIs do not contain propellants and are breath-actuated (Kaplan and Price 2018). |
| Formulation | Drug substance dissolved or suspended in a propellant, a mixture of propellants, or a mixture of solvents, propellants and other excipients. FDA also calls MDIs inhalation aerosols. | FDA calls DPI formulations inhalation powders. |
| Main components | Container closure system: canister, actuator and metering valve, plus optional features such as an integrated spacer or integrated dose counter (FDA draft guidance). Kaplan and Price describe a pressurized canister, a chamber for producing an aerosol, and a mouthpiece. | A device constituent part that holds or receives the powder formulation: individual containers (capsules, blisters, cartridges, dosing discs) for pre-metered DPIs, or an internal reservoir for device-metered DPIs (FDA draft guidance). |
| How the dose is metered | By the metering valve in the container closure system. | Pre-metered DPIs contain previously measured amounts of formulation in individual containers that are inserted into the device. Device-metered DPIs hold enough formulation for multiple doses in a reservoir and the device meters each dose during use. |
| Breath actuation and flow | Older push-activated MDIs require coordinated breathing and actuation; newer models are breath-actuated (Kaplan and Price 2018). | Breath-actuated. Many DPIs need a minimum inspiratory flow rate; power-assisted "active" DPIs also exist (Kaplan and Price 2018). |
| Spacer compatibility | A spacer or valved holding chamber can be attached to a pMDI; this makes the assembly bulkier, and electrostatic charge can reduce output (Kaplan and Price 2018). An MDI container closure system can also have an integrated spacer. | The sources read do not describe spacers as an accessory for DPIs. FDA classification product code NVO defines a spacer as a device used with nebulizers and metered dose inhalers. |
| FDA classification | A drug-device combination product. Stand-alone spacers are regulated by CDRH as Class 2 devices (21 CFR 868.5630, product code NVO); spacers that replace an MDI actuator and dose counters are frequently determined to be device components of the combination product (FDA jurisdictional update, 2020). | Also a combination product: the FDA jurisdictional update states that it applies equally to dry powder inhalers. Product code QKS covers drug-led (CDER or CBER) metered dose and dry powder inhalers. |
| Related design: soft mist inhaler | Differs from an MDI: a soft mist inhaler (for example Respimat) uses spring power rather than stored liquefied gas, and has no propellant. | Differs from a DPI: a soft mist inhaler delivers a slow-moving fine liquid aerosol, not a powder, and is not breath-actuated (Kaplan and Price 2018). |
| Which one suits whom | This is a design comparison, not a recommendation. The choice of inhaler device is made by a prescriber with the patient. | This is a design comparison, not a recommendation. The choice of inhaler device is made by a prescriber with the patient. |
| Source | FDA draft guidance on MDI and DPI products (fda.gov/media/70851/download); FDA jurisdictional update on metered dose inhalers, spacers and other accessories (page current as of 12 Feb 2020); openFDA device classification, read 30 Oct 2026. | Kaplan A, Price D. Matching Inhaler Devices with Patients: The Role of the Primary Care Physician. Can Respir J 2018;2018:9473051 (pmc.ncbi.nlm.nih.gov/articles/PMC5989279/); same FDA sources, read 30 Oct 2026. |
Common questions
Common questions about MDI (pressurized metered dose inhaler) vs DPI (dry powder inhaler)
What is a metered dose inhaler?
+
A metered dose inhaler (MDI) is an inhalation aerosol product. FDA describes its container closure system as a canister, an actuator and a metering valve, holding a drug dissolved or suspended in a propellant or a mixture of solvents, propellants and excipients. FDA treats MDIs as drug-device combination products.
What are the types of dry powder inhaler?
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FDA draft guidance describes two types. Pre-metered DPIs contain previously measured amounts of formulation in individual containers such as capsules, blisters, cartridges or dosing discs, which are inserted into the device. Device-metered DPIs have an internal reservoir with enough formulation for multiple doses, and the device meters each dose during use. Power-assisted "active" DPIs also exist.
What is a soft mist inhaler?
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A soft mist inhaler, such as Respimat, uses spring power to deliver a slow-moving fine liquid aerosol. It contains no propellant and is not breath-actuated, which separates it from both MDIs and DPIs (Kaplan and Price 2018).
What are the types of inhaler spacer?
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The sources describe three arrangements. A stand-alone spacer is a reservoir with an open mouthpiece, used with nebulizers and metered dose inhalers; CDRH regulates it as a Class 2 device (21 CFR 868.5630). A valved holding chamber is a related attachment for pMDIs. An integrated spacer is built into the MDI container closure system. A spacer that replaces an MDI actuator is a device component of the combination product.
Are MDIs and DPIs regulated as drugs or devices?
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Both are drug-device combination products according to FDA. Some accessories are regulated separately: general-use stand-alone spacers are devices under CDRH, while dose counters and actuator-replacing spacers are frequently determined to be device components of the combination product.
Going deeper
